Problem: Evaluate the following expression when $x = 7$ and $y = 9$. $6$ $x$ $ + 3$ $y$ $ - 6$
Solution: Substitute $7$ for ${x}$ and $9$ for ${y}$ $ = 6{(7)} + 3{(9)} - 6 $ $ = 42 + 27 - 6 $ $ = 63$